The invention relates to the field of server virtualization and network storage. Computer system virtualization techniques allow one computer system, referred to as a host system, to execute virtual machines emulating other computer systems, referred to as guest systems. Typically, a host computer runs a hypervisor or other virtualization application. Using the hypervisor, the server computer may execute one or more instances of guest operating systems simultaneously on the single host computer. Each guest operating system runs as if it were a separate computer system running on physical computing hardware. The hypervisor presents a set of virtual computing resources to each of the guest operating systems in a way that multiplexes accesses to the underlying physical hardware of a single host computer.
One application of virtualization is to consolidate server computers within data centers. Using virtualization, multiple distinct physical server computers, each running its own set of application services, can be consolidated onto a single physical server computer running a hypervisor, where each server is mapped onto a virtual machine (VM) running on the hypervisor. In this approach, each VM is logically independent from the others and each may run a different operating system. Additionally, each VM is associated with one or more virtual storage devices, which are mapped to onto one or more files on a file server or one or more logical units (LUNs) on a storage area network (SAN).
Consolidation of server computers using virtualization reduces administrative complexity and costs because the problem of managing multiple physical servers with different operating systems and different file systems and disks is transformed into a problem of managing virtual servers on fewer physical servers with consolidated storage on fewer fileservers or SANs.
Large organizations, such as enterprises, are often geographically spread out over many separate locations, referred to as branches. For example, an enterprise may have offices or branches in New York, San Francisco, and India. Each branch location may include its own internal local area network (LAN) for exchanging data within the branch. Additionally, the branches may be connected via a wide area network (WAN), such as the internet, for exchanging data between branches.
Although virtualization allows for some consolidation of server computers and associated storage within a branch location, the latency, bandwidth, and reliability limitations of typical wide-area networks prevents the consolidation of many types of server computers and associated storage from multiple branch locations into a single location.
Because the WAN connecting branches is much slower than a typical LAN, storage access for clients and server applications at a branch location performing large or frequent data accesses via a WAN is unacceptably slow. Therefore, server and storage consolidation using prior virtualization techniques is unsuitable for these applications. For example, if a client or server application at a branch location frequently accesses large amounts of data from a database or file server, the latency and bandwidth limitations of accessing this data via the WAN makes this data access unacceptably slow. Therefore, system administrators must install and configure servers and data storage at the branch location that are accessible by a LAN, which is typically faster than a WAN by several orders of magnitude. This incurs additional equipment and administrative costs and complexity.
Additionally, WAN connections are often less reliable than a LAN. WAN unreliability can adversely affect the delivery of mission-critical services via the WAN. For example, an organization may include mission-critical operational services, such as user authentication (e.g., via Active Directory) or print services (e.g., Microsoft Windows Server Print Services). Prior server and storage virtualization is unsuitable for consolidating mission-critical operational services at a central location, such as a data center, because if the WAN connection is disabled or intermittently functioning, users can no longer access printers or log in to their computers.
Because of the performance limitations of WANs, organizations have previously been unable to consolidate time-critical, mission-critical, and/or data intensive servers and data storage from multiple branches into a single location, such as a data center. Installing and configuring, referred to as deploying, and maintaining file servers and data storage at a number of different branches is expensive and inefficient. Organizations often require on-site personnel at each branch to configure and upgrade each branch's data storage, and to manage data backups and data retention. The deployment of servers, data storage, and the local area network connecting the servers, data storage, and clients at new branches (or migrating existing branches to new locations) is complex and time-consuming. Additionally, organizations often purchase excess computing and storage capacity for each branch to allow for upgrades and growing data storage requirements. Because branches are serviced infrequently, due to their numbers and geographic dispersion, organizations often deploy enough computing and data storage at each branch to allow for months or years of growth. However, this excess computing and storage capacity often sits unused for months or years until it is needed, unnecessarily driving up costs.
Therefore, there is an unmet need for reducing the equipment and administrative costs and associated complexity of operating time-critical, mission-critical, and/or data intensive servers at branch locations. Additionally, there is an unmet need to reduce the time and complexity for deploying servers, data storage, and local area networks at new and relocated branch locations.